1. Field of the Invention
The present invention concerns a device for counting and analysing particles or aerosols suspended in air.
2. Description of the Prior Art
Advantageously not but exclusively, it combines in a device for analysing a gas composition by means of flame spectrophotometry, for example of the type described in the patent FR No. 98 00761 filed in the name of the Applicant.
Generally speaking, it is known that flame spectrophotometry is a method consisting of conducting a spectrographic analysis of the radiation produced by the flame of a gas mixture including the elements to be analyzed and an oxidant gas, such as hydrogen. This analysis is effected by isolating the characteristic radiations of the sought-after elements and by measuring these radiations by photometric means.
So as to be able to apply this method to certain elements which do not generate any characteristic light emission, it is necessary to provoke prior to combustion a reaction of these elements with a reactive element so as to obtain a compound producing an identifiable and detectable light emission.
This prior reaction can be effected out by carrying out a first combustion in the presence of a reactive agent.
The gas mixture derived from this first combustion is subjected to a second combustion which produces a light emission for which the spectrophotometric analysis is also carried out.
This spectrophotometric detection can be associated with a detection of ionisation of the flame by means of electrodes placed in the combustion chamber of the burner. These electrodes are connected to an electronic circuit for measuring the conductivity of the zone where combustion occurs.
This measurement makes it possible to detect the presence of combustible constituents in the sample and in particular organic materials: the combustion of this organic material in fact produces between the measuring electrodes an ionisation current in relation with the organic material concentration.
The information delivered by the spectrophotometric assembly and detection of ionisation can be sent to a processor programmed so as to interpret this information and deduce from it sought-after element concentrations, whether they be compounds, chemical substances or even biological substances (bacteria).
In fact, in the case where the gas sample to be analyzed contains suspended particles, these particles on burning generate light impulses (flash) of limited period which it is possible to count so as to obtain the number of particles per unit of gas volume to be analyzed.